Your Nuchal Translucency (NT) Scan
‘Nuchal translucency refers to the normal subcutaneous fluid-filled space between the back of the fetal neck and the overlying skin’
Dr. Furgul D. Malone, Women’s Health & Education Centre
Why do I need a nuchal translucency scan?
The main purpose of an NT scan is to acquire a measurement of the fluid at the back of your baby's neck. This measurement is used to calculate a risk factor for several chromosomal abnormalities – the most well known of which is Down syndrome. About 75% of trisomy 21(Down syndrome) foetuses have increased nuchal thickness. Other general and structural anatomy will also be checked during this scan. If this is your first scan, it will be used to accurately date your pregnancy.
When should a nuchal translucency scan be performed?
An NT scan is performed between 11 weeks and 13 weeks-6 days. The timing is very important; the scan can only be performed at this stage due to development of the nuchal fold (the fluid at the back of the baby’s neck).
How is the scan performed?
The scan is generally performed over your abdomen (tummy), but depending on several factors (including your size and the position of the womb/baby), it may be necessary to perform an internal scan. This involves placing a small probe inside the vagina (which generally provides a clearer image). If this is necessary, the sonographer will explain what is involved and will gain your consent prior to performing this scan.
Is the measurement hard to obtain?
To acquire this measurement the baby has to be in a very specific position. It’s quite common for babies to be uncooperative so you might be asked to go for a walk to change the baby's position. Sometimes it might be necessary to return on a different day if the measurement can’t be obtained, but this is fairly common and nothing to worry about.
Frequently Asked Questions
Q. Will I find out if the neck measurement is normal during the scan?
A. No: The measurement is sent to a lab where it's entered into a software package along with your blood results, age, and various other data to generate a risk factor.
Q. Will this test tell me if my baby has Down syndrome?
A. No: This test will only give you an idea whether you have a high or a low risk. Even with a low risk there is still a small chance of having a baby with a chromosomal abnormality. This test is designed to identify women at high risk so they can be offered further tests (such as amniocentesis) that will give them a definite answer.
Q. Can I bring other people with me?
A. Most places are happy for you to bring at least one person with you, although this may vary depending on your country and the practice you attend. If you do bring more people, please bear in mind that the sonographer/doctor will need to concentrate, and several people (or noisy children) can be distracting. Please consider also that although this is usually an enjoyable experience, if there is a problem, it may be difficult to process this information when you have children with you.
Q. Can I find out the baby’s sex at this scan?
A. Some sonographers may tell you what they think, although due to the development at this stage, it can be unreliable. It's often better to wait until your 18–20 week scan when things are a little clearer (although still not 100%).
Q. Can I use video or take photos during the scan?
A. This may vary between countries and practices. Generally, it's not allowed because it's a diagnostic medical procedure. You'll be given at least one picture at most practices and will often have the opportunity to receive images via email, on USB, or on Compact Disc.
For More Information
The Fetal Medicine Foundation contains a great deal of information on nuchal translucency scans, including the measurements the sonographer/doctor will acquire
The Women's Health & Education Centre has an excellent section on the NT scan, and much more
